In relation to domestic cat body shape, cobby is the opposite to slender (‘oriental’ in the cat world). It describes a shape which is stocky, sturdy, rounded, short legged, short muzzle etc.. The best way to visualise a cobby cat body is to think the opposite of slender and ‘elegant’.
I have a page on the body conformations of the cat breeds. The Selkirk Rex is ‘semi-cubby’ meaning somewhat rounded and stocky. The Manx, Burmese, Persian and Exotic Shorthair are cobby cats.
The picture on this page is of a Cymric, which is a longhaired Manx. The Cymric has a cobby body shape.
P.S. A cobby body can apply to other animals. It is not used to describe people. Cobby shaped people are referred to as ‘stocky’. Cat breeders create cobby cats using selective breeding.
Dictionary definition of ‘stocky’ – broad and sturdily built.